Solvability of matrix-exponential equations

Conference item

We consider a continuous analogue of (Babai et al. 1996)’s and (Cai et al. 2000)’s problem of solving multiplicative matrix equations. Given k + 1 square matrices A1, . . . , Ak, C, all of the same dimension, whose entries are real algebraic, we examine the problem of deciding whether there exist non-negative reals t1, . . . , tk such that Yk i=1 exp(Aiti) = C. We show that this problem is undecidable in general, but decidable under the assumption that the matrices A1, . . . , Ak commute. Our results have applications to reachability problems for linear hybrid automata. Our decidability proof relies on a number of theorems from algebraic and transcendental number theory, most notably those of Baker, Kronecker, Lindemann, and Masser, as well as some useful geometric and linear-algebraic results, including the MinkowskiWeyl theorem and a new (to the best of our knowledge) result about the uniqueness of strictly upper triangular matrix logarithms of upper unitriangular matrices. On the other hand, our undecidability result is shown by reduction from Hilbert’s Tenth Problem.

Authors: Ouaknine, J; Pouly, A; Sousa Pinto, J; Worrell, J

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Association for Computing Machinery
• Host title: LICS '16 Proceedings of the 31st Annual ACM/IEEE Symposium on Logic in Computer Science
• Pages: 798-806
• Publication date: 2016-07-05
• Acceptance date: 2016-04-04
• DOI: 10.1145/2933575.2934538
• ISBN: 9781450343916
• Keywords: hybrid automata; matrix reachability; exponential matrices; matrix logarithms; commuting matrices